A conventional capacitive dynamical quantity sensor device is disclosed in JP-A-11-326365 (referred to as Patent Publication 1). The sensor device includes movable electrodes for being displaced in a predetermined direction in accordance with the application of a dynamical quantity, and stationary electrodes arranged to confront the movable electrodes, on one face side of a semiconductor substrate.
A general top plan construction of a sensor chip 100 in that capacitive dynamical quantity sensor device is shown in FIG. 6. FIG. 7 is a schematic section of the capacitive dynamical quantity sensor device, and shows the state, in which the sensor chip 100 is laminated and mounted over a circuit chip 200, in a section taken along line VII—VII of FIG. 6.
In this sensor chip 100, a semiconductor substrate 10 is trench-etched from its one face side to form trenches, thereby forming a movable portion composed of a beam portion 22 and movable electrodes 24 integrated with the former, and stationary electrodes 30 and 40 confronting the movable electrodes 24.
The beam portion 22 has a spring function to be displaced in the directions of arrow Y in FIG. 6 in accordance with the application of a dynamical quantity, and has a beam shape to extend in the direction perpendicular to the displacing directions Y. The movable electrodes 24 are formed integral with the beam portion 22 and are arrayed in plurality in the comb tooth shape along the displacing directions Y of the beam portion 22, so that they can be displaced together with the beam portion 22 in the displacing directions Y.
The stationary electrodes 30 and 40 are fixed and supported by the substrate 10 and are arrayed in plurality in such a comb tooth shape as to mesh with the spacings of the comb teeth in the movable electrodes 24. The side faces of the stationary electrodes 30 and 40 and the side faces of the movable electrodes 24 are arranged to confront each other.
The movable electrodes 24 and the individual stationary electrodes 30 and 40 are connected with wiring portions 25, 32 and 42, respectively. At predetermined positions over the wiring portions 25, 32 and 42, respectively, wire bonding pads 25a, 30a and 40a are formed.
Moreover, the individual pads 25a, 30a and 40a are electrically connected with the circuit chip 200 through bonding wires W1, W2 and W3, respectively. Here, FIG. 7 shows the connection mode by the bonding wire W1 exclusively for the pad 25a of the movable electrode 24, but the remaining pads 30a and 40a have similar connection modes.
Here, the capacity to be established in the spacing (or the electrode spacing) between the movable electrode 24 and the stationary electrode 30 on the left-hand side of FIG. 6 is designated by CS1, and the capacity to be established in the spacing (or the electrode spacing) between the movable electrode 24 and the stationary electrode 40 on the right hand is designated by CS2.
In this sensor chip 100, moreover, the capacities CS1 and CS2 between the left-hand and right-hand movable electrodes 24 and the stationary electrodes 30 and 40 change according to the application of the dynamical quantity. A signal based on that capacity difference (CS1−CS2) is outputted as an output signal from the sensor chip 100 and is processed in the circuit chip 200 and finally outputted. The dynamical quantity is thus detected.
However, in such a capacitive dynamical quantity sensor, only one stationary electrode 30 or 40 is arranged for each of the comb-toothed movable electrodes 24 as shown in FIG. 6.
An improvement in the sensitivity is desired for the capacitive dynamical quantity sensor device. Accordingly, the capacity between the movable electrodes and the stationary electrodes must be increased. For the increase in the capacity between the movable electrodes and the stationary electrodes, moreover, it is sufficient to enlarge the opposed areas between those electrodes.
Therefore, the inventors have contemplated increasing opposed areas between the electrodes by arranging two stationary electrodes in a manner to confront one of the comb-toothed movable electrodes. This contemplated design is shown in FIG. 8 and is labeled Related Art.
Specifically, each of the stationary electrodes 30, 31, 40 and 41 is arranged to confront each of one and other sides of the individual movable electrodes 24 along the comb tooth arraying direction of the movable electrodes 24. This construction of two stationary electrodes will be called the “two-side stationary electrode construction”.
However, this two-side stationary electrode construction has an increased number of stationary electrodes. If the electrodes are to be led out for the wire bonding operation, the pattern for the lead-out wiring portions becomes complicated. On the other hand, the wiring portions could be formed in the substrate to lead out the electrodes. However, the structure is also complicated.
It is, therefore, conceivable that a wire boding could be done for each of the stationary electrodes 30, 31, 40 and 41 thereby to connect the result wires W and the circuit chip, as shown in FIG. 8. The circuit chip is omitted from FIG. 8.
In this case, however, the large number of wires W also complicates the construction. Therefore, this construction is not preferable because the wire bonding is hard or because the adjoining wires W may make contact with each other.